ref: 9745060db687df6fb74d0487d4cc401cba61982d
parent: 95e2bf7e4c8dae6bd1fd96b73a96afaf5c64f1e5
author: Jean-Marc Valin <[email protected]>
date: Thu Feb 10 11:06:06 EST 2011
Minor draft update (CELT)
--- a/doc/draft-ietf-codec-opus.xml
+++ b/doc/draft-ietf-codec-opus.xml
@@ -92,18 +92,6 @@
that is CBR by using all the bits left unused by the SILK layer.
</t>
-<t>The implementation of SILK-based LP layer is similar to the description in
-the <xref target="SILK">SILK Internet-Draft</xref> with the main exception that
-SILK was modified to
-use the same range coder as CELT. The implementation of the CELT-based MDCT
-layer is available from the CELT website and is a more recent version
-(0.11.0)
-of the <xref target="CELT">CELT Internet-Draft</xref>.
-The main changes
-include better support for 20 ms frames as well, the ability to encode
-only the higher bands using a range coder partially filled by the SILK
-layer, and a pre-/post- filter used to aid coding of highly tonal signals.</t>
-
<t>
In addition to their frame size, the SILK and CELT codecs require
a look-ahead of 5.2 ms and 2.5 ms, respectively. SILK's look-ahead is due to
@@ -941,9 +929,8 @@
<section anchor="normalization" title="Bands and Normalization">
<t>
-The MDCT output is divided into bands that are designed to match the ear's critical bands,
-with the exception that each band has to be at least 3 bins wide for the
-smallest (2.5ms) frame size and the larger frame sizes use integer
+The MDCT output is divided into bands that are designed to match the ear's critical
+bands for the smallest (2.5ms) frame size. The larger frame sizes use integer
multiplies of the 2.5ms layout. For each band, the encoder
computes the energy that will later be encoded. Each band is then normalized by the
square root of the <spanx style="strong">non-quantized</spanx> energy, such that each band now forms a unit vector X.